1. The Field of the Invention
The present invention relates to descrambling television signals. More specifically, the present invention relates to descrambling scrambled television signals at an electronics device in an entertainment system using a cable box to verify that the viewer has been granted access to the descrambled signals.
2. The Prior State of the Art
In today""s society, people are spending more time watching television. The demand for more television has led to the creation and development of television channels dedicated to news, sports, movies and special events. A few of these channels, including those affiliated with the major networks, are free and viewers can receive these channels by simply erecting and connecting an antenna to their television. The downside of using an antenna is that only a few channels can be received and the reception is not always clear. In order to receive a larger selection of television channels, the viewer must subscribe to services offered by a cable or satellite television provider.
When a viewer subscribes to television services from a cable or satellite operator, the viewer typically selects a television channel package. The least expensive package usually contains a basic set of television channels, while the more expensive packages contain premium television channels, examples of which include movie channels and pay-per-view programming. Premium channels are typically scrambled and consumers pay an additional amount in order to be able to descramble and view those channels. Those consumers that do not choose the more expensive television channel packages receive the premium channels in the scrambled and unviewable format. In some cities, some or all of the basic television channels are scrambled in addition to premium channels.
In many instances, a viewer needs a cable box in order to receive cable television channels. The cable box receives signals corresponding to all of the cable television channels, but is configured to descramble only the premium channels that the consumer has purchased. When a viewer subscribes to, modifies, or cancels cable service, the cable operator programs the cable box to descramble the appropriate channels. Cable boxes can be programmed manually by a technician or remotely by sending a conditional access signal from the cable head end to the cable box.
While cable boxes perform important functions, such as those described above, they introduce complexity into home entertainment systems, particularly when combined with other consumer electronics devices, such as video tape recorders or set top boxes (STBs) that provide access to the Internet or other services. One problem is related to the act of changing channels. For example, if a cable box is connected to certain types of set top boxes and the consumer desires to change the channel, a code is sent to the STB and then relayed to the cable box. The cable box then tunes the channel and, if necessary, descrambles the channel so that the user may view the selected channel. In other words, every time a person wants to change channels, the signal must be relayed, thereby introducing delay into the process. If a user selects a specific channel, the process of relaying a command signal might be executed repeatedly. For example, if a user selects channel 104, four codes are relayed to the cable box: the digits xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d, xe2x80x9c4xe2x80x9d and the enter command.
Adding to this delay is the fact that many cable boxes include hardware or software that is outdated. While newer technologies can change, tune and descramble channels faster than many legacy cable boxes, cable operators often find it infeasible to replace such cable boxes with newer ones. The combination of these factors results in a noticeable delay when a person is rapidly changing channels or channel surfing. Further delay can be introduced by some legacy cable boxes that are incapable of skipping unused channels as the user incrementally advances through the channels in the television signal.
Another concern, from the point of view of the cable television provider, is that there are publicly accessible algorithms that permit viewers to descramble many or all scrambled television signals without authorization to do so. The availability of such descrambling algorithms permits viewers to have access to and view scrambled television channels without payment. It would be desirable, therefore, to enable scrambled signals to be descrambled using newer and faster technology without merely replacing legacy cable boxes with new cable boxes. It would be particularly desirable to provide such efficient descrambling capabilities while conforming to access control measures implemented by cable and satellite television providers to allow only authorized subscribers to receive premium channels.
The present invention relates to descrambling television signals in a device other than the traditional cable box, while using conditional access settings contained in a viewer""s cable box to authenticate that the viewer has been granted permission to receive the descrambled channels. In this manner, signal descrambling can be conducted using efficient algorithms and new, relatively fast processors without the risk of the viewer gaining access to unauthorized channels. Cable operators do not need to replace legacy cable boxes with new ones, but can continue to use existing cable boxes as authenticators for the right of the viewers to receive the descrambled channels.
According to one implementation of the invention, in order to determine whether a viewer is authorized to view descrambled channels, the descrambling device (i.e., the electronics device in which descrambling is to be performed) periodically causes the cable box to cycle through at least some of the scrambled channels in the cable television signal. The descrambling device monitors the output signal of the cable box and determines, for each scrambled channel, whether the cable box has generated a descrambled signal. When the cable box outputs a descrambled signal, the descrambling device determines that the cable box is capable of descrambling the scrambled channel and infers that the cable television provider has granted the viewer access to the channel. Conversely, when the cable box outputs a scrambled channel, the descrambling device determines that the cable box is not capable of descrambling the scramble channel and infers that the cable television provider has not granted the viewer access to the channel. In this manner, the descrambling device uses the existing cable box as an authenticator for the right of the viewer to access particular scrambled channels. Based on the results of the foregoing authentication process, the descrambling device is enabled to descramble the channels to which the viewer has been granted access and is disabled from descrambling the channels to which the viewer has not been granted access.
The authentication process can be repeated as desired to remain current with any change in the subscription status of the viewer. For instance, the process can be performed daily during the early morning hours or at another time that is unlikely to interfere with the viewing habits of the user. After the authentication process, when the viewer, by means of a remote control device or otherwise, issues a command to tune to a scrambled channel, the descrambling device rather than the cable box descrambles the channel, assuming that the descrambling device has determined that the viewer is authorized to receive the channel. Thus, scrambled signals are descrambled using the relatively fast descrambling hardware and software of the descrambling device, thereby reducing the delay that might otherwise be present, while preserving the ability of the cable operator to impose conditional access to premium channels.
The invention can advantageously include further techniques to prevent viewers from circumventing the authentication process. As described above, the authentication process relies on monitoring the output signal of the cable box to determine whether it includes a scrambled or descrambled signal. Theoretically, a particularly persistent user could tamper with the authentication process by replacing the scrambled output of the cable box with a non-scrambled, albeit different, television signal. Without some further security measures, the descrambling device might falsely interpret the substituted, non-scrambled signal as an indication that the user is authorized to access the scrambled channel.
In order to detect such attempts to breach the security features of the invention, the descrambling device can compare the timing of cyclical characteristics of a known instance of a particular descrambled signal with the cyclical characteristics of the output signal of the cable box. For example, the descrambling device descrambles a particular scrambled signal and monitors the timing of the vertical blanking interval or another selected cyclical characteristic of the signal. During the authentication process, the cable box outputs a non-scrambled channel that is supposedly the same as the aforementioned channel that has been descrambled by the descrambling device (but not yet conclusively the same in view of the possibility that the user has tampered with the process). The descrambling device monitors the timing of the vertical blanking interval or another corresponding cyclical characteristic of the non-scrambled output signal. If the two signals are synchronized, it is highly probable that the two signals are the same and that there has been no attempt to circumvent the authentication process, whereas non-synchronization indicates possible user interference.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.